Euphorbia virosa grows in a vast area from the Orange river (South Africa) to the north of Namibia and South Angola. It is a slow-growing but vigorous wide-branching cactus-like shrub or small tree with angled, upright, leafless and spiny stems, forming fairly dense clumps of growth, up to 1-1.5 metres, occasionally to 3 metres across and high; the numerous branches usually arise in whorls from the base conferring it a candelabra-like shape which is similar in appearance to the unrelated organ pipe cacti of the Americas. The plant is protected against over-heating by its irregular stem and light thorns that reflect the sunlight. It is well named, the "venomous euphorbia," for the virulent poison of its milky latex, an effective defence against most herbivores

Common names: Poison Tree, Gifboom, poisonous spurge

Stem: Main stem (trunk) very short at most 30 cm in diameter, divided into large numbers of basal whorled, spreading and curved ascending branches, rarely rebranched 50-60(-70) mm thick, in the lower part 3-angled, often spiral, in the upper part 5-8-angled, grey-green, with a bluish tint, probably glaucous, and constricted at short but irregular intervals in a series of joints 50-90 mm length, so that the angles appear to be broadly scolloped. Angles irregular, not spirally twisted, separated by concave channels about 2 cm deep, slightly sinuate-toothed almost bent at right angles. Stems are adapted for water storage and covered in a thick cuticle which reduces water loss.
Ribs: Vertical or slightly spiralling, (5-)7(-8) divided by sharp-angled grooves to 10 mm deep, angles with sinuate teeth.
Stipular spines: Spine pairs, dark red and shiny when young, becoming grey or brownish-grey with darker tips, joined in a continuous horny margin 4-4 mm broad, 6-12 mm apart, ferocious, sharp, widely diverging, straight or slightly curved, upward-pointing up to 4-13 mm long.
Leaves: Rudimentary, transverse, about 1 mm long and 4 mm broad, truncate, soon deciduous. In habitat the few very small leaves of E. virosa appear in summer (January), and the conditions are therefore most favourable for transpiration and surface-evaporation during the hottest months.
Inflorescence: The inflorescence is a solitary, subsessile cyme seated 4-6 mm above the spine-pairs and nearer the pair of spines above them.
Flowers (cyathia): Up to 1 cm in diameter. Nectar glands elliptic, yellow and touching.
Blooming season (south Africa): The flowers are produced mostly at the end september, and beginning of October (in northern hemisphere spring)
Fruit: Smallish about 1-1,5 cm, fleshy, rusty-brown hardening at maturity.
Seeds: Globose about 5 mm in diameter and finely rugose.